BDNF and major depressive disorder: In addition, BDNF levels and depression symptoms showed no significant correlations between the normal (r = 0.24, t = 0.71, df = 8, and p = 0.4) and depressed groups (r = 0.01, t = 0.07, df = 17, and p = 0.9), and HARS correlations showed similar results.